In the world, there are many kinds of outlets having different specifications, i.e., receptacles of different shapes. In a case where products for export are manufactured, each product is provided with a plug suitable for the specification of the product's destination, or each product is provided with a conversion plug as disclosed in U.S. Pat. No. 5,613,863 or Japanese Laid-open Patent Publication No. 2007-52998 at the time of shipment.
Here, when a plug manufacturer produces plugs, it is cost-effective to assemble: a plug suitable for the specification of one kind of outlet; and a conversion plug used as an adaptor of the plug and suitable for another kind of outlet, rather than separately producing each plug for the specification of a suitable outlet. This is because the attachment plug usually has various circuits including an AC-DC conversion circuit and an overcurrent prevention circuit and thus, in many cases, the cost as a whole is reduced by mounting such circuits on only an attachment plug of one kind and making a conversion plug serve only for the purpose of supporting an outlet of different specification.
Therefore, in such a system that a plug assembly is exported after being formed by securely coupling an attachment plug and a conversion plug to each other, the plug assembly can be provided at a lower cost.
Here, when forming a plug assembly composed of an attachment plug and a conversion plug, the following are important. Blades and the like to be inserted into an outlet should be protected from unintentional force applied thereto without, extra caution when the conversion plug is inserted into the attachment plug. Also, after the conversion plug is coupled to the attachment plug, the conversion plug and the attachment plug should be so integrated that there is no backlash or play between the coupled attachment plug and conversion plug, thereby preventing deformation of the blades.